Multi-layer ceramic substrate and method for manufacture thereof

ABSTRACT

A plurality of first green sheets forming first ceramic layers after firing are stacked to form a first pre-fired substrate  4 . Next, a plurality of second green sheets forming second ceramic layers after firing are stacked to form a second pre-fired substrate. Next, the first pre-fired substrate  4  is formed with recesses  10 . Next, first pre-fired blocks  6  of sizes fitting into the recesses are formed from the second pre-fired substrate. The first pre-fired blocks  6  are fit into the recesses  10  so that the stacking direction A of the first green sheets and the stacking direction A′ of the second green sheets become the same. The first pre-fired substrate  4  in which the first pre-fired blocks  6  are fit is fired.

TECHNICAL FIELD

The present invention relates a multilayer ceramic substrate comprisedof a combination of a plurality of ceramic materials having mutuallydifferent electrical characteristics and/or physical characteristics anda method of production of the same.

BACKGROUND ART

A multilayer ceramic substrate is comprised of a plurality of ceramiclayers. The ceramic layers have formed between them, following alongtheir interfaces, interconnect conductors. Usually, a multilayer ceramicsubstrate is made multifunctional and sophisticated in performance byproducing it by stacking green sheets of a plurality of types of ceramicmaterials having mutually different electrical characteristics orphysical characteristics and simultaneously firing the obtainedcomposite stack. This is for building into the multilayer ceramicsubstrate capacitors, inductors, and other electronic devices requiringdifferent dielectric constant characteristics etc.

However, if stacking and simultaneously firing green sheets of aplurality of types of ceramic materials having mutually differentelectrical characteristics or physical characteristics, the differencesin shrinkage behavior of the green sheets of the different ceramicmaterials etc. will cause cracking or peeling in some cases.

To resolve this problem, for example, Patent Document 1: Japanese PatentPublication (A) No. 2001-144438 proposes a multilayer ceramic substratecomprised of dielectric ceramic materials having mutually differentdielectric constants stacked together, wherein interdiffusion betweenlayers and shrinkage of the multilayer ceramic substrate are preventedby the method of providing shrinkage suppressing green sheets betweenthe layers.

However, in the method described in Patent Document 1, the thicknessesof the shrinkage suppressing green sheets themselves are added on. Ontop of this, to form devices complying with the dielectric constants inthe principal plane directions of the layers, sufficient thicknesses ofthe layers have to be secured. For this reason, the thickness of themultilayer ceramic substrate as a whole increases. This runs counter tothe demands for increasing compactness of electronic equipment.

Note that Patent Document 2: Japanese Patent Publication (A) No.11-163530 discloses technology forming a space inside a stack ofpre-fired green sheets, fitting into that space a pre-fired shapedarticle block, then simultaneously firing the shaped article block andstack of green sheets.

However, the technology described in Patent Document 2 has the stackingdirection of the stack forming the pre-fired shaped article blocksubstantially perpendicular to the stacking direction of the greensheets in which this shaped article block is inserted. Consequently,there is the problem that at the time of firing, the shaped articleblock easily detaches from the stack of the green sheets. For thisreason, in the technology described in Patent Document 2, it isnecessary to insert the shaped article block into the stack of the greensheets, then sandwich this by non-shrinkable sheet-shaped supports notbeing fired at the firing temperature of the green sheets so as to firethe stack of the green sheets.

DISCLOSURE OF THE INVENTION

The present invention was made in consideration of this actual situationand has as its object the provision of a multilayer ceramic substratewhere the different layers do not have any effect on each other, thethickness of the multilayer ceramic substrate as a whole is sharplysuppressed, and formation of devices is facilitated.

To achieve the above object, the method of production of a multilayerceramic substrate according to the present invention comprises the stepsof:

-   -   stacking a plurality of first green sheets forming first ceramic        layers after firing so as to form a first pre-fired substrate,    -   stacking a plurality of second green sheets forming second        ceramic layers after firing so as to form a second pre-fired        substrate,    -   forming a recess in said first pre-fired substrate,    -   forming from said second pre-fired substrate a first pre-fired        block of a size fitting in said recess,    -   fitting said first pre-fired block into said recess so that a        stacking direction of said first green sheets and a stacking        direction of said second green sheets become the same, and    -   firing said first pre-fired substrate in which said first        pre-fired block is fit.

In the method of production of a multilayer ceramic substrate accordingto the present invention, first pre-fired substrate at the side to befit into and the first pre-fired block at the side for fitting into itare respectively formed by stacking green sheets of the same materials,so there is little peeling between layers or cracking at the time offiring. Further, since the stack of the first ceramic layers and thestack of the second ceramic layers with mutually different dielectricconstants are positioned respectively independently in the substrate andsufficient thicknesses are secured, it is possible to form electronicdevices matching those dielectric constants.

For example, a location having a relatively large dielectric constant(block or substrate) may be formed with capacitor devices, while alocation having a relatively small dielectric constant (block orsubstrate) may be formed with inductor devices etc., i.e., the freedomof design is secured. Further, even if the shrinkages of the substratematerials differ somewhat at the time of firing, since the stackingdirection of the block and the stacking direction of the substrate arethe same, the tendencies for shrinkage are also the same and thereforethe fired block will not detach from the fired substrate. Further, sinceinterconnects formed on the surface of the substrate are used to connectthe members, this as well means that the fired block will not detachfrom the fired substrate.

Preferably, said first pre-fired block is not formed with terminals atits side faces and said first pre-fired block is formed with terminalsat its top surface and/or bottom surface. Since the block is not formedwith terminals at its side faces, there is no need for connection withthe substrate at the side faces of the block. Further, at the topsurface and/or bottom surface of the block, it is possible to connectwith surface electrodes of the substrate through the terminals. Further,since the block is not formed with terminals at its side faces, thereare no internal conductor layers present near the side faces of theblock and therefore there is no problem even if differences in materialsbetween the block and substrate etc. cause a reaction to occur at theside faces of the block at the time of firing.

Preferably, said recess is a through hole passing through said firstpre-fired substrate from a top surface to a bottom surface. Said throughhole may have fit into it together with said first pre-fired block asecond pre-fired block different from said first pre-fired block.Alternatively, said recess may be a closed-end hole not passing throughsaid first pre-fired substrate from a top surface to a bottom surface.The depth and structure of the recess may be freely designed inaccordance with the size, number, etc. of the devices to be built intothe block. Further, by fitting inside the recess the other secondpre-fired block, it is possible to house blocks having differentdielectric constants inside the same recess.

Preferably, said first green sheets and second green sheets arecomprised of materials giving different dielectric constants afterfiring. Alternatively, the first green sheets and second green sheetsare comprised of the same material but made different in thickness.Preferably, the thicknesses of said first green sheets forming saidfirst pre-fired substrate are greater than the thicknesses of saidsecond green sheets. For example, the thicknesses of the second greensheets forming the block in which devices are to be built are preferablythin from the viewpoints of reducing the size and raising theperformance of the devices. Further, the thicknesses of the first greensheets in which devices are not to be built, but where simpleinterconnect layers etc. are to be built are preferably greater from theviewpoint of reducing the stacking step.

Preferably, said first green sheets and/or said second green sheets haveinternal conductor layers interposed between them. These internalconductor layers form interconnect layers or internal electrodes ofbuilt in devices etc.

Preferably, said first green sheets and said second green sheets havethe same extents of press shrinkage and firing shrinkage. In this case,when pressing or firing the first pre-fired substrate in which the firstpre-fired block is fit, peeling between the block and substrate orcracks etc. can be more effectively suppressed.

In the present invention, it is preferable to fit said first pre-firedblock into the recess of said first pre-fired substrate, then fire saidfirst pre-fired substrate and connect the terminals formed at thesurface of the fired substrate and the terminals formed at the surfaceof the fired block by interconnects.

Alternatively, it is possible to fit said first pre-fired block into therecess of said first pre-fired substrate, then connect the terminalsformed at the surface of the first pre-fired block and the terminalsformed at the surface of said first pre-fired substrate byinterconnects, then fire said first pre-fired substrate.

The multilayer ceramic substrate of the present invention is produced byany of the above methods of production. Note that the multilayer ceramicsubstrate according to the present invention may be used alone as afinished product or the multilayer ceramic substrate may have otherelectronic devices attached to it.

BRIEF DESCRIPTION OF THE DRAWINGS

Below, the present invention will be explained based on embodimentsshown in the drawings.

FIG. 1 is a schematic cross-sectional view showing a step of productionof a multilayer ceramic substrate according to an embodiment of thepresent invention,

FIG. 2 is a schematic cross-sectional view showing a step after FIG. 1,

FIG. 3 is a schematic cross-sectional view of a first pre-fired blockshown in FIG. 1,

FIG. 4 is a plan view of the first pre-fired block shown in FIG. 3,

FIG. 5 is a plan view of state after printing the surface of the firedsubstrate with circuit patterns and connecting the terminals of theblock and terminals of the substrate to predetermined patterns,

FIG. 6A and FIG. 6B are schematic cross-sectional views of multilayerceramic substrates according to other embodiments of the presentinvention embodiment

First Pre-fired Substrate

As shown in FIG. 1, in the method of production of a multilayer ceramicsubstrate according to one embodiment of the present invention, first afirst pre-fired substrate 4 is prepared. The first pre-fired substrate 4is produced by stacking a plurality of first green sheets forming afirst ceramic layer after firing in a thickness direction A, thentemporarily press bonding this in the stacking direction A. The firstgreen sheets are, in accordance with need, formed with internalconductor layers between them.

When stacking the first green sheets and internal conductor layers, ifusing the printing method, it is sufficient to print successive layersof dielectric paste and the internal conductor paste on a polyethyleneterephthalate or other substrate. Further, if using the sheet method, itis sufficient to use dielectric paste to form green sheets, printingthese with the internal conductor paste, then stack these.

The thickness of the first pre-fired substrate 4 is not particularlylimited, but for example is 0.4 mm to 1.5 mm or so. The shape of thefirst pre-fired substrate 4 is not particularly limited, but in thisembodiment, is a square shape of 25 mm×25 mm. The pressure of thetemporary press bonding is not particularly limited, but preferably is 3to 8 MPa or so. The heating temperature at that time is 50 to 100° C. orso.

The thickness of the individual first green sheets is determined by thedevices, interconnects, etc. to be built into the first substrate 40shown in FIG. 2 obtained by firing the first pre-fired substrate 4 orother applications and generally is 20 to 245 μm or so. For example, inthe case of an application where it is desired to build a large numberof inductors into the first substrate 40, the thickness of the firstgreen sheets is preferably made small. Further, in the case of forminghigh Q-value interconnects in the first substrate 40 or in the case offorming heat dissipating via holes etc., the first green sheets arepreferably made thick. The number of the first green sheets stacked isnot particularly limited, but is 4 to 50 or so.

The first green sheets are fabricated from dielectric paste. Thedielectric paste is comprised of a dielectric material and an organicvehicle kneaded together and may be an organic-based coating or awater-based coating.

The dielectric material used is one which forms a main ingredient andsub ingredient in accordance with the ingredients of the dielectricceramic composition. Note that the form of the materials is notparticularly limited. Oxides forming the main ingredients and subingredients and/or compounds giving these oxides upon firing are used.These materials may be powder obtained by liquid-phase synthesis, thesolid-phase method, etc.

Note that as compounds giving oxides upon firing, for example,carbonates, nitrates, oxalates, organometallic compounds, etc. may bementioned by way of illustration. Of course, oxides may also be usedtogether with compounds giving oxides upon firing. The contents of thecompounds in the dielectric material should be determined so as to givethe ingredients of the dielectric composition explained above afterfiring.

The “organic vehicle” means a binder dissolved in an organic solvent.The binder used for the organic vehicle is not particularly limited, butethyl cellulose, polyvinyl butyral, or other usual types of binders maybe suitably selected from. Further, the organic solvent used at thistime is also not limited. Terpineol, butyl carbitol, acetone, toluene,or other organic solvents may be suitably selected from in accordancewith the printing method, sheet method, or other method used.

Further, the “water-soluble coating” means a water-soluble binder,dispersant, etc. dissolved in water, while the “water-soluble binder” isnot particularly limited and may be suitably selected from polyvinylalcohol, cellulose, water-soluble acrylic resin, emulsion, etc.

The internal conductor paste is prepared by kneading conductivematerials comprised of the above-mentioned various types of conductivemetals or alloys or various types of oxides giving the above-mentionedconductive materials after firing, organometallic compounds, resinates,etc. and the above-mentioned organic vehicle.

The content of the organic vehicle of each of the above-mentioned pastesis not particularly limited and may be an ordinary content, for example,it may include the binder in an amount of 1 to 5 wt % or so and thesolvent in an amount of 10 to 50 wt % or so. Further, each paste maycontain, in accordance with need, additives selected from various typesof dispersants, plasticizers, dielectrics, insulator, etc.

Second Pre-Fired Substrate and First Pre-Fired Block

Next, the second pre-fired substrate is prepared. The size and thicknessof the second pre-fired substrate is the same as the first pre-firedsubstrate 4. The method of making the second pre-fired substrate is alsosimilar to that of the first pre-fired substrate 4. However, in thepresent embodiment, the dielectric material of the second green sheetsforming the second pre-fired substrate or the sheet thicknesses are madedifferent from those of the first green sheets forming the firstpre-fired substrate 4. Further, the second green sheets have formedbetween them, for example, inductor devices, capacitor devices, LCcomplex circuit devices, filter circuit devices, and other devices andpatterns for making interconnects among these devices.

Note that preferably the dielectric material included in the dielectricpaste forming the second green sheets can be fired at the sametemperature as the dielectric material included in the dielectric pasteforming the first green sheets and has the same extent of pressshrinkage and firing shrinkage. As combinations satisfying thesecharacteristics, for example, the combinations of the followingcompositions of materials may be mentioned by way of illustration.

For example, when the composition of the dielectric material of thefirst green sheets is an aluminum oxide-based dielectric material (SiO₂in 26.45 wt %, B₂O₃ 1.76 wt %, Al₂O₃ 55.37 wt %, MgO 0.86 wt %, CaO 1.59wt %, and SrO 13.97 wt %), the composition of the dielectric material ofthe second green sheets may be the compositions as shown next, that is,an aluminum oxide-titanium oxide-based dielectric material (SiO₂ in32.62 wt %, B₂O₃ 2.18 wt %, Al₂O₃ 25.35 wt %, MgO 1.06 wt %, CaO 1.97 wt%, SrO 17.23 wt %, and TiO₂ 19.60 wt %), an aluminum oxide-titaniumoxide-strontium oxide-based dielectric material (SiO₂ in 9.05 wt %,Al₂O₃ 9.21 wt %, La₂O₃ 19.63 wt %, B₂O₃ 2.21 wt %, BaO 8.79 wt %, TiO₂23.42 wt %, Bi₂O₃ 4.56 wt %, Nd₂O₅ 20.61 wt %, and SrO 1.73 wt %), astrontium feldspar-α-quartz-based dielectric material (SiO₂ in 66.60 wt%, B₂O₃ 12.71 wt %, Al₂O₃ 9.20 wt %, Sb₂O₃ 5.33 wt %, CaO 1.61 wt %, SrO3.12 wt %, ZnO 0.81 wt %, and MgO 0.56 wt %), an aluminumoxide-α-quartz-based dielectric material (BaO in 24.59 wt %, Al₂O₃ 19.05wt %, SiO₂ 53.94 wt %, and B₂O₃ 2.42 wt %), an osmium oxide-titaniumoxide-based dielectric material (BaO in 20.21 wt %, Nd₂O₃ 36.81 wt %,TiO₂ 37.73 wt %, B₂O₃ 1.42 wt %, CuO 0.95 wt %, and ZnO 1.90 wt %), etc.are preferable.

After the second pre-fired substrate is prepared, next this secondpre-fired substrate is cut or punched to predetermined sizes to obtainthe first pre-fired blocks 6 shown in FIG. 1. The first pre-fired blocks6 are not particularly limited, but for example are sizes of 1 mm to 10mm square. The thicknesses are the same as the thickness of the firstpre-fired substrate 4. Note that the top surfaces and/or back surfacesof the first pre-fired blocks 6, as shown in FIG. 3 and FIG. 4, areformed with terminals 8. The terminals 8 are formed by printing etc.external terminal paste the same as the internal conductor paste. Theterminals 8 may be formed at the stage of the second pre-fired substrateor may be formed at the stage of the blocks. As shown in FIG. 5, the topsurface and/or bottom surface of the first pre-fired substrate 4 is alsoformed with terminals 36. These terminals 36 are in a later stepconnected by interconnects 38 to predetermined circuit patterns.

Formation of Recess, Fitting, and Firing

Separate from the steps for fabricating the first pre-fired blocks 6from the second pre-fired substrate, the first pre-fired substrate 4 isformed with through holes (recesses) 10 passing through it from the topto bottom surface by for example punching. The through holes 10 areslightly larger in size than the size of the first pre-fired blocks 6.As shown in FIG. 1, each through hole 10 is fit with a correspondingfirst pre-fired block 6. The top surfaces and bottom surfaces of thefirst pre-fired blocks 6 are substantially planar with the top surfaceand bottom surface of the first pre-fired substrate 4. Note that, asshown in FIG. 3, each first pre-fired block 6 is comprised of aplurality of green sheets 30 stacked in the thickness direction A′. Thelayers of the green sheets 30 have internal electrode layers 32interposed between them in predetermined patterns. These internalelectrode layers 32 and terminals 8 are connected by via holes 34 etc.In this embodiment, the first pre-fired blocks 6 are fit in the throughholes 10 so that the stacking direction A′ of the green sheets 30 of thefirst pre-fired blocks 6 becomes same as the stacking direction A of thegreen sheets in the first pre-fired substrate 4 shown in FIG. 1.

After this, the first pre-fired substrate 4 in which the first pre-firedblocks 6 are fit is pressed in the stacking direction. The pressure isnot particularly limited, but is preferably 40 to 100 MPa or so. Theheating temperature is about 35 to 80° C. or so. After this, the firstpre-fired substrate 4 is treated to remove the binder and fired togetherwith the first pre-fired blocks 6 whereby the multilayer ceramicsubstrate 2 comprised of the fired first substrate 40 and blocks 60shown in FIG. 2 is obtained.

The firing temperature is determined by the material of the green sheetsetc. and is not particularly limited, but in general is 850 to 1000° C.Further, the firing atmosphere may be suitably determined in accordancewith the type of the conductive material in the internal conductorpaste. When using as the conductive material Ni or an Ni alloy or otherbase metal, a reducing atmosphere is preferable. The oxygen partialpressure of the firing atmosphere is preferably 10⁻¹⁰ to 10⁻³ Pa, morepreferably 10⁻⁷ to 10⁻³ Pa. If the oxygen partial pressure at the timeof firing is too low, the conductive material of the internal electrodeswill be liable to be abnormally sintered and to break, while if theoxygen partial pressure is too high, the internal electrodes will tendto be oxidized.

After this, as shown in FIG. 5, the first substrate 40 is printed on itssurface with circuit patterns, and the terminals 8 of the blocks 60 andthe terminals 36 of the first substrate 40 are connected byinterconnects 38 to predetermined patterns. Note that the circuitpatterns may be printed before firing the first substrate 40 as well.

In the method of production of the multilayer ceramic substrate 2according to the present embodiment, since the first pre-fired substrate4 at the side to be fit in and the first pre-fired blocks 6 at the sideto fit into it are comprised of green sheets of the same materialsstacked together, at the time of firing, there is little peeling oflayers, cracks, etc. Further, since the stack of the first substrate 40and the stack of the blocks 60 with the mutually different dielectricconstants are positioned in the substrate independently and sufficientthicknesses can be secured, electronic devices matching with theirdielectric constants can be formed.

For example, a location having a relatively large dielectric constant(block 60 or first substrate 40) may be formed with capacitor devices,while a location having a relatively small dielectric constant (block 60or substrate 40) may be formed with inductor devices etc., i.e., thefreedom of design is secured. Further, even if the shrinkages of thesubstrate materials differ somewhat at the time of firing, since thestacking direction A′ of the first pre-fired blocks 6 and the stackingdirection A of the first pre-fired substrate 4 are the same, thetendencies for shrinkage are also the same and therefore the firedblocks 60 will not detach from the fired first substrate 40. Further,since interconnects 38 formed on the surface of the first substrate 40are used to connect the members, this as well means that the firedblocks 60 will not detach from the fired first substrate 40.

Other Embodiments

Note that the present invention is not limited to the above-mentionedembodiment and may be modified in various ways within the scope of thepresent invention.

For example, as shown in FIG. 6A, the first pre-fired substrate 4 a maybe formed in its surface with closed end holes 10 a of different depthsnot passing through the substrate from its top to bottom surfaces. Firstpre-fired blocks 6 a matching the sizes of the closed end holes 10 a maybe fit into them. The top surfaces of the first pre-fired blocks 6 a aresubstantially planar with the surface of the first pre-fired substrate 4a. The rest of the steps are similar to those of the embodiment shown inFIG. 1 to FIG. 5.

This embodiment exhibits actions and effects similar to those of theembodiment shown in FIG. 1 to FIG. 5. Further, since first pre-firedblocks 6 a having dielectric constants and other electricalcharacteristics different from those of the first pre-fired substrate 4a are built into the substrate at the minimum necessary parts of themultilayer ceramic substrate, the freedom of design is further increasedand the substrate is made compacter.

Further, in the present invention, as shown in FIG. 6B, the firstpre-fired substrate 4 b may also be formed with a plurality of throughholes 10 and at least some of the through holes 10 may be fit, togetherwith the first pre-fired blocks 6 b, with other second pre-fired blocks20. The second pre-fired blocks 20, for example, are blocks havingdifferent dielectric constants or other electrical characteristics fromthe first pre-fired blocks 6 b or blocks comprised of green sheets ofthicknesses different from the thicknesses of the green sheets formingthe first pre-fired blocks 6 b. The rest of the steps are similar tothose of the embodiment shown in FIG. 1 to FIG. 5.

This embodiment exhibits actions and effects similar to those of theembodiment shown in FIG. 1 to FIG. 5. Further, since blocks 6 b and 20having dielectric constants and other electrical characteristicsdifferent from those of the first pre-fired substrate 4 b can be builtinto the substrate, the freedom of design is further increased and thesubstrate is made compacter.

Further, in the present invention, the pre-fired substrates 4, 4 a, and4 b in which these blocks 6, 6 a, 6 b, and 20 are embedded may also bestacked as is, without firing, with other pre-fired substrates and thenfired.

As explained above, according to the present invention, it is possibleto provide a multilayer ceramic substrate where the different layers donot have any effect on each other, the thickness of the multilayerceramic substrate as a whole is sharply suppressed, and formation ofdevices is facilitated. Further, in the present invention, since thestacking direction of the green sheets in the fit blocks and thestacking direction of the green sheets in the substrate into which theblocks are fit are the same, there is no need for non-shrinkablesheet-shaped supports at the time of firing and the blocks can be madeintegral with the substrate so as not to detach after firing.

1. A method of production of a multilayer ceramic substrate comprisingthe steps of: stacking a plurality of first green sheets forming firstceramic layers after firing so as to form a first pre-fired substrate,stacking a plurality of second green sheets forming second ceramiclayers after firing so as to form a second pre-fired substrate, forminga recess in said first pre-fired substrate, forming from said secondpre-fired substrate a first pre-fired block of a size fitting in saidrecess, fitting said first pre-fired block into said recess so that astacking direction of said first green sheets and a stacking directionof said second green sheets become the same, and firing said firstpre-fired substrate in which said first pre-fired block is fit.
 2. Themethod of production of a multilayer ceramic substrate as set forth inclaim 1, wherein said first pre-fired block is not formed with terminalsat its side faces and said first pre-fired block is formed withterminals at its top surface and/or bottom surface.
 3. The method ofproduction of a multilayer ceramic substrate as set forth in claim 1,wherein said recess is a through hole passing through said firstpre-fired substrate from a top surface to a bottom surface.
 4. Themethod of production of a multilayer ceramic substrate as set forth inclaim 3, wherein said through hole fits said first pre-fired block and asecond pre-fired block different from said first pre-fired block.
 5. Themethod of production of a multilayer ceramic substrate as set forth inclaim 1, wherein said recess is a closed-end hole not passing throughsaid first pre-fired substrate from a top surface to a bottom surface.6. The method of production of a multilayer ceramic substrate as setforth in claim 1, wherein said first green sheets and second greensheets are comprised of materials giving different dielectric constantsafter firing.
 7. The method of production of a multilayer ceramicsubstrate as set forth in claim 1, characterized in that said firstgreen sheets and second green sheets are different in thicknesses. 8.The method of production of a multilayer ceramic substrate as set forthin claim 7, characterized in that the thicknesses of said first greensheets forming said first pre-fired substrate are greater than thethicknesses of said second green sheets.
 9. The method of production ofa multilayer ceramic substrate as set forth in claim 1, wherein saidfirst green sheets and/or said second green sheets have internalconductor layers interposed between them.
 10. The method of productionof a multilayer ceramic substrate as set forth in claim 1, characterizedby fitting said first pre-fired block into the recess of said firstpre-fired substrate, then firing said first pre-fired substrate andconnecting terminals formed on the surface of said fired substrate andterminals formed on the surface of the fired block by interconnects. 11.The method of production of a multilayer ceramic substrate as set forthin claim 1, characterized by fitting said first pre-fired block into therecess of said first pre-fired substrate, then connecting terminalsformed on the surface of said first pre-fired block and terminals formedon the surface of said first pre-fired substrate by interconnects, thenfiring said first pre-fired substrate.
 12. The method of production of amultilayer ceramic substrate as set forth in claim 1, wherein said firstgreen sheets and said second green sheets have the same extents of pressshrinkage and firing shrinkage.
 13. The multilayer ceramic substrateobtained by a method of production as set forth in claim 1.